Sumner, how do I build more complicated expressions?
Through the symbol palette or the keyboard, you can enter numbers, variables and math symbols.
Let's enter this equation now.
First, type in "2 * ".
OK, Sumner, you know there's no square root on my keyboard!
To add the square root, click on the square root button on the symbol palette and type "16".
If you don't leave the radical, Mathcad will keep adding to the number under the radical.
Wait, we don't want to add 1 under the radical, we want to add 1 outside the radical.
To leave the radical, you need to press the spacebar. 
Notice that the box, called the selection box, encloses the operator and everything it applies to.
Now that you have left the radical, type "+ 1", and you are adding 1 outside the radical.
To divide everything by 3, press the spacebar to select it.
Now press the "/" key and type 3.
You need to press the spacebar to select the entire equation before you can add 1.
Now press "=", and there's your answer!
What if I want to remove the radical?
There are two ways to remove the radical. You can click to the right of the 16 and get the insertion bar. Then press the spacebar.
Or, you can click directly on the radical. This selects the radical and the value beneath it.
Now press Delete.
How would I subtract 1 from the end of the equation rather than adding 1?
Simply click on the + sign and press Delete.
Now type "-". Mathcad inserts a - sign into the placeholder. Click outside the math region to see the new answer.
So all I have to do to edit operators is click on the operator I want to change.
Let's enter another equation.
To add an exponent, click on the exponent button in the operator palette.
Press the spacebar to leave the exponent.
Type "+ 1" and press "=" to evaluate the equation.
So, if I hadn't pressed the spacebar, I would have added 1 to the exponent.
That's right. Watch...I'll use the arrow keys to move back to the exponent.
If I add 1 now, it is added to the exponent.